SAN ANTONIO – The combination of topical 5% imiquimod plus systemic nanoparticle albumin-bound paclitaxel showed excellent clinical efficacy and was well tolerated for the treatment of cutaneous metastases of breast cancer in a phase II study.
Among the 11 patients who were able to complete the novel combined chemoimmunotherapy regimen, 5 had a complete response, meaning 100% clearance of treated skin lesions at week 24.
In addition, one patient had a partial response, defined as a greater than 50% reduction in the size of the largest treated lesion. Four patients had stable disease, with less than 50% reductions in lesion size. One patient experienced progressive disease, with a 25% increase in target lesion size, Dr. Lupe G. Salazar reported at the San Antonio Breast Cancer Symposium.
Fifteen heavily pretreated breast cancer patients were enrolled in the single-arm, nonrandomized study. All had skin metastases no longer amenable to standard therapies.
The chemoimmunotherapy regimen consisted of three treatment cycles. Each 4-week cycle consisted of application of topical 5% imiquimod to target cutaneous lesions on 4 days per week plus systemic albumin-bound paclitaxel (Abraxane) at 100 mg/m2 on days 1, 8, 15, and 28, explained Dr. Salazar of the University of Washington, Seattle.
Treatment-related toxicities included neutropenia, lymphopenia, anemia, nausea, and fatigue; 34% of toxicities were grade 1, 56% were grade 2, and the remaining 10% were grade 3.
Four of 15 subjects were unable to complete the treatment regimen, having withdrawn due to progression of visceral disease.
The rationale for the imiquimod plus nanoparticle albumin-bound (nab) paclitaxel (Abraxane) therapy derives from previous evidence that imiquimod, a toll-like receptor-7 agonist, has shown clinical efficacy against cutaneous metastases. Imiquimod stimulates secretion of Th1 cytokines and upregulates immune costimulatory molecules at the tumor site. Tumor-specific T cell immunity and tumor growth inhibition are enhanced. Moreover, paclitaxel has been shown to increase serum interferon-gamma levels and boost natural killer cell activity. Thus, the working hypothesis was that nab-paclitaxel would augment imiquimod’s antitumor effects, according to Dr. Salazar.
She and her coinvestigators examined the combination therapy’s impact upon endogenous tumor-specific immunity. They obtained pre- and posttreatment 2-mm skin biopsies from target lesions and were able to demonstrate that the treatment marginally enhanced endogenous immunity to the well-known breast cancer antigens HER2, p53, melanoma-associated antigen 3 (MAGE-3), insulin growth factor binding protein-2 (IGFBP-2), and topoisomerase IIa (TOPO-IIa).
The study was funded by a grant from the National Cancer Institute. Dr. Salazar declared having no relevant financial interests.